Seismic Response Analysis of a Semi-active-controlled Base ...

Table 3 Estimated system parameters of the entire building based on the N4SID methodDirection ModeNatural Frequency [Hz]Damping factor20-60 s 100-150 s 200-300 s 20-60 s 100-150 s 200-300 sNS 1st 0.48 0.31 0.32 0.141 0.180 0.132direction 2nd 1.66 1.42 1.49 0.110 0.0626 0.303EW 1st 0.48 0.31 0.32 0.263 0.166 0.158direction 2nd 1.46 1.38 1.41 0.110 0.0760 0.0782Table 4 Estimated system parameters of the superstructure of the building based on the N4SID method7th floorDirection ModeNatural Frequency [Hz]Damping factor20-60 s 100-150 s 200-300 s 20-60 s 100-150 s 200-300 sNS 1st 1.13 0.86 0.83 0.043 0.019 0.050direction 2nd 2.15 2.12 2.91 0.036 0.067 0.057EW 1st 1.04 0.90 0.83 0.037 0.081 0.040direction 2nd 2.70 2.51 2.70 0.024 0.099 0.0531st floorBaseisolationlayer1st mode 2nd mode 1st mode 2nd modea) NS direction b) EW directionFig. 3 Estimated 1st and 2nd mode shapes for the time interval from 100 to 150 s(solid: real, dashed: imaginary)RESTORING FORCE PROPERTIES OF THE ISOLATION LAYERThe restoring force properties of the isolation layer are calculated. Since relative displacementsrecords were not measured in the main shock, the relative displacements of the isolation layer arederived based on acceleration records at the foundation slab and the 2nd basement floor using doubleintegral and a Butterworth filter considering causality. The Lissajous figure of the relativedisplacements of the isolation layer is indicated in Fig. 4.1028